1. Field
Aspects of the present invention relate to an organic light emitting device, a lighting apparatus including the organic light emitting device, and an organic light emitting display apparatus including the organic light emitting device, and more particularly, to an organic light emitting device having an increased outcoupling efficiency, a lighting apparatus including the organic light emitting device, and an organic light emitting display apparatus including the organic light emitting device.
2. Description of the Related Art
An organic light emitting device includes an organic emissive layer disposed between electrodes that are opposite to each other. An electron generated by one electrode and a hole generated by the other electrode are recombined in the organic emissive layer. At this time, emissive molecules of the organic emissive layer are excited by the recombination. Then, the emissive molecules revert back to a ground state while simultaneously light is emitted.
Generally, light emitted from the organic emissive layer of the organic light emitting device has no predetermined directivity. Light is emitted in random directions having a statistically homogeneous angular distribution. Thus, a ratio of the actual number of photons reaching an observer to the total number of photons generated by the organic emissive layer of the organic light emitting device (that is, outcoupling efficiency (ηout)) may vary according to refractive indexes of layers included in the organic light emitting device, but is no more than about 15 to 20%.
The outcoupling efficiency of an organic light emitting device limits overall quantum efficiency (EQE) and power efficiency of the organic light emitting device. The EQE and power efficiency are factors used to determine overall power consumption and lifetime of the organic light emitting device. Therefore, various efforts to increase the outcoupling efficiency have been made.